steam than the simple type: triple and quadruple engines should not be considered.
Superheated steam will lead to economy in a simple engine equal to that obtained with saturated steam in a compound. The engine and piping must be especially designed for the superheat used.
DIAGNOSIS AND TREATMENT OF FEED WATER IMPURITIES1
Symptom Cause Remedy
Priming or foaming. . . Organic matter causing a scum to gather on the surface of the water Carbonate of soda Blow down frequently. Use settling tank, filter and coagulant (alum or iron alum). Blow down. If contained in water, treat with barium carbonate. If introduced as a feature of chemical treatment, change treatment.
Corrosion ........... Acids in water or formed Carbonate of soda.
from ingredients in water (as from salt water) Organic matter Air in feed water Chloride and sulphate of magnesium Electrolysis Filter with coagulant. If from grease, use carbonate of soda. Employ mineral cylinder oils. Exclude or liberate air. Heat feed. Add caustic soda or slacked lime. Put zinc plates in boiler. Carbonate of soda. Zinc plates.
Mud, sediment. . . . Suspended matter Blow down. Settling tanks ni-
Scale .......... Soluble salts Blow down
Bicarbonates of lime, magnesium, etc. Sulphate of lime Heat feed to 212° and filter. Use lime or lime and soda or barium carbonate. Live steam feed water heating. Soda or barium carbonate.
1 An interesting application of mass action is the use of the socalled artificial zeolites in water softening. A perfect zeolite would be NaaO.AhOaCSiOh.CHaO. When a water containing magnesium and calcium sulphates or bicarbonates is passed through a bed of zeolites, the sodium in the zeolite'is replaced by the calcium or magnesium and sodium sulphate or carbonate is left in the water. These salts do not form scale. To regenerate the zeolites a strong solution of common salt is passed the bed